Process and device for the fabrication of alloys

ABSTRACT

A PROCESS FOR MAKING ALLOYS IS DISCLOSED WHEREIN THE ALLOYING IS CARRIED OUT IN A VACUUM OF AT LEAST 10**-4 TORR. ONE OF THE SUBSTITUENTS IS IN IONIZED VAPOR FORM AND IS DEPOSITED UPON A VERTICALLY PLACED SUBSTRATE CONTAINING THE REST OF THE ALLOY INGREDIENTS. THE SUBSTRATE IS KEPT AT A TEMPERATURE EQUAL TO THE MELTING POINT OF THE DESIRED ALLOY WHICH FALLS BY GRAVITY INTO A CONTAINER.

March 6, 1973 E. VANDERSCHUEREN PROCESS AND DEVICE FOR THE FABRICATION 0F ALLOYS Filed April 24, 1970 2 Sheets-Sheet 1 INVENTORS EMILE VANDERSCHUEREN :2 ATTORNEYS March 6, 1973 E. VANDERSCHUEREN 3,719,470

PROCESS AND DEVICE FOR THE FABRICATION OF ALLOYS Filed April 24, 1970 2 Sheets-Sheet 2 INVENTORS EMILE VANDERSCHUEREN ATTORNEYS United States Patent Int. Cl. C22b 9/14; C21c 7/10; C22e 1/00 US. C]. 75-65 2 Claims ABSTRACT OF THE DISCLOSURE A process for making alloys is disclosed wherein the alloying is carried out in a vacuum of at least torr. One of the substituents is in ionized vapor form and is deposited upon a vertically placed substrate containing the rest of the alloy ingredients. The substrate is kept at a temperature equal to the melting point of the desired alloy which falls by gravity into a container.

The invention relates to a process for the production of alloys, and especially, but not exclusively, of alloys the composition of which is accurate and contains a minimum of impurities. The invention also relates to apparatus for performing this process. A large number of techniques are known for the production of alloys, but they are all relatively complex to operate as soon as the alloys or their constituents have to have a high degree of purity (or require the absence of certain impurities) and when a high degree of accuracy is required in respect of the quantitative composition of the alloy or in the distribution of the constituents.

According to the present invention, the alloys are made in a vacuum of at least 10- torr from constituents, at least one of which is supplied in the form of an ionised vapour while the or an other or others is supplied in the form of a solid phase on which the ionised vapour phase constituent is deposited so as to form the required alloy on the surface of the solid-phase component in the form of liquid drops which fiow by gravity from the said surface.

The apparatus for performing this invention is characterised by a vacuum chamber in which it is possible to produce a vacuum of 10 torr, and in which a vapour concentration chamber is disposed, whose electrically earthed walls can be heated to the rebound temperature of the said vapour, the said chamber surrounding a vapour source consisting of one of the constituents of the required alloy, and a substrate consisting of the other component, and beneath which a mould is situated, the said substrate being provided with means for bringing it to an electrical potential attracting the said ionised vapour and with means for bringing it to the melting temperature of the required alloy, the said chamber also being provided with one or more apertures for the passage of one or more electron beams issuing from one or more electron guns disposed in the vacuum chamber outside the vapour chamber.

The method of producing alloys uses a vacuum of at least 10* torr. At least one of the alloy constituents is supplied in the form of a vapour from a block locally heated to boiling temperature, the vapour preferably being ionised. This vapour is deposited on a block of solid material forming the other constituent, after the style of thin film deposits on substrates. The block of solid material acting as the substrate is heated to the melting temperature of the required alloy. The lowest temperature at which the substrate can be heated is the "Ice temperature of the eutectic formed from the constituents used, when such eutectic exists. This eutectic forms on the surface of the substrate from which it flows just by gravity. All that remains is to collect it in a mould. If the substrate is heated to a higher temperature, the drops of alloy forming on its surface are distributed between the constituents, the distribution being identical to that corresponding to the temperature of the substrate on the state diagram. One of the great advantages of this invention is, therefore, that the composition of the alloy can be adjusted simply by adjusting the temperature of the substrate according to the point of the state diagram corresponding to the distribution required between the alloy constituents.

The substrate is advantageously brought to a suitable electrical potential to attract the ionised vapour. In a preferred but not exclusive embodiment of the invention, the potential is between 10 and volts depending upon the element present in the vapour phase. When the vapour is ionised by an electron beam, this potential is positive, i.e. the substrate must then be at a potential which is 10 to 150 volts higher (depending upon the source material) than that of the source from which the vapour issues.

The effect of this potential is that the ionised atoms of the vapour are attracted to the substratein preference to other atoms having a different optimum attraction potentialand this effect occurs even inside the substrate over a distance of several lattice planes of its crystal lattice. This potential is therefore very advantageous in that it reduces the introduction from the vapour phase of impurities into the alloy. It enables vapour sources to be used in cases in which the material to be evaporated need not necessarily have an unduly high degree of purity.

The substrate may consist of a block of a single material or of a block of alloy already containing the constituents required for the final alloy, and in the required proportions, minus the constituent supplied in vapour form. The ionised vapour phase may itself contain various constituents in which case the vapour source is formed by a plurality of sources each emitting just one of the constituents to be deposited on the substrate to form the alloy. Each of the sources can be individually at a potential 10 to 150 volts less than that of the substrate, depending on its nature. The content of the various constituents in the alloy can always be adjusted by selecting the appropriate substrate temperature. However, it can also be adjusted by adjusting the amount of vapour issuing from each source, and the source-substrate potential in respect of each source.

The process according to the invention provides a number of advantages including the possibility of producing very pure alloys, the content of the various constituents of which can be very easily adjusted without any complex operations.

Two specific embodiments of apparatus for carrying out the process of the invention and the use of the apparatus will now be described, by way of example, with reference to the accompanying drawings in which:

FIGS. 1 and 2 are perspective views of two examples of apparatus which employ, respectively one and two source's of vapour of constituents of the required alloy.

In each case the apparatus is disposed inside a vacuum chamber (not shown) in which it is possible to produce a vacuum of the order of 10- torr.

The apparatus shown in FIG. 1 comprises a substrate 1 made from one of the constituents (which may itself already be an alloy), a source 2 of the other constituent, and a mould 3 disposed beneath the substrate 1 so as tocollect the drops of alloy forming on its surface, flowelectrically conductive. The mould is electrically earthed.

The block 2 may also be dis-posed on a vertical rotary shaft 4 so that the heat introduced into the block 2 can be distributed more satisfactorily, provided that the electron beam does not impinge on the centre of the surface 5. It is thus possible to form a disc or pool 7 of material in the liquid state on the surface 5, where the said liquid is brought to boiling point.

In order to prevent any loss of vapour issuing from the source 2, the latter together with the substrate is disposed inside a chamber 6, the walls of which are heated to the rebound temperature of the atoms issuing from the source, i.e. the temperature at which the vapour atoms colliding with the walls rebound from the latter and are therefore still available solely for the substrate. The chamber 6 has a small aperture 8 through which an electron beam directed onto the surface can penetrate from an electron gun disposed in the vacuum chamber which contains the chamber 6.

The chamber 6 and the source 2 are electrically earthed, while the substrate 1 is connected to a positive potential which is variable between and 150 volts and which is supplied by a generator 9 and a potentiometer 10. The beam leakage electrons and the secondary electrons emitted by the source ionise the vapour.

In order to reduce the risk of any undesirable substance being introduced into the vapour during the starting stages, the walls of the chamber 6 are advantageously made from the same material as the block 2.

FIG. 2 shows an apparatus which is similar to the apparatus shown in FIG. 1 but in which the source 2 comprises two elementary sources (2, 2') each emitting vapour of one of the constituents of the required alloy in the pure state. The chamber 6 comprises elementary chambers 6 and 6 each having an aperture 8, 8' for the passage of a concentrated heating and ionisation electron beam. Each of the elementary chambers is advantageously made from the same material as that of the source which it surrounds, and is earthed.

The above chambers are connected at the level of the substrate 1 so that the latter has parts of its surface in each of the chambers. In this case the substrate 1 is rotated about a vertical axis so that every point on its surface is successively presented to all the constituents of the ionised vapour phase. The constituent content of the resulting alloy may be adjusted by varying the surface of the substrate 1 exposed at any time to the vapour from each chamber, by disposing the chambers so that the substrate 1 penetrates into the same with the required surface area. Composition adjustments may also be made by varying the energy supplied to the different vapour sources by the electron beams.

The sources are also at electrical potentials which are 10 to 150 volts lower than that of the substrate, the potentials being individually adjustable by means of potentiometers 11 and 11.

Without departing from the scope of the invention, it is also possible to make the apparatus with more than two sources and two chambers.

I claim:

1. A process for the production of alloys comprising supplying at least one of the alloy constituents in ionized vapor form in a vacuum of at least 10 torr, supplying the remainder of the alloy constituents in the form of a vertically placed substrate whereupon the ionized vapor phase constituent is deposited to form the desired alloy on the surface of the substrate, maintaining the substrate at a temperature equal to the melting temperature of the desired alloy, and allowing the alloy to flow in liquid form by gravity into a container. 2. The process of claim 1 including connecting the substrate to an electrical potential to attract the ionized vapor.

References Cited UNITED STATES PATENTS 3,554,739 1/ 1971 Bickerdike -135 3,528,902 9/1970 Kiyotaka Wasa 204-492 3,514,388 5/1970 Brumfield 204-192 3,574,565 4/1971 Paine 1l7l07 3,535,103 10/1970 Whitfield 75-135 HYLAND BIZOT, Primary Examiner P. D. ROSENBERG, Assistant Examiner US. Cl. X.R. 7549, 

